Oil cyst (breast)
Updates to Article Attributes
Oil cysts in breast imaging refer to benign breast lesions where an area of focal fat necrosis becomes becomes walled off by fibrous tissue.
Epidemiology
Occurs across all age and ethnic groups with a female predilection. Usually associated with blunt trauma if present in males.
Clinical presentation
-
Nonusually asymptomatic - tender or non-tender palpable lump
-
asymptomaticbruising, if recent trauma
Pathology
Fat debris from ruptured lipocytes tends to conglomerate to form a macroscopic pool of oil surrounded by lipid-laden macrophages or foam cells - known as an oil cyst. The wall can then calcify. Most often this occurs secondary to trauma or surgery; however, this is not always necessary.
Aetiology
The aetiology of oil cysts is felt to be most often an end-form of liquefaction fat necrosis of the breast resulting from trauma or surgery. However, some oil cysts arise independently, without a prior history of trauma or surgery.
Macroscopic appearance
Specimens are usually obtained from surgical excision or aspiration. Grossly, appears as viscous, oily fluid/material.
Microscopic appearance
Fat-filled macrophages and foreign body giant cells are usually present. There may be haemorrhage into fat. A fibrous capsule forms around the lipid contents. Following fatty acid saponification, there may be calcific precipitation.
Associations
- multiple intradermal oil cysts can be part of steatocystoma multiplex
Radiographic features
Mammography
Typically seen as a radiolucent rounded mass of fat density +/- wall calcification, which if present typically appears as eggshell calcification. Lesions are usually well circumscribed with a thin capsule. Rarely, fat-fluid levels may be present.
Ultrasound
On ultrasound, most oil cysts are hypo-echoic with smooth walls and show neither posterior acoustic enhancement or shadowing. AEchogenicity varies. Fat-fluid levels are better characterised sonographically. When present, rim calcifications will demonstrate posterior acoustic shadowing. Complex features include thick walls, mural nodularity, and internal echoic bands. A very small proportion can represent an intracystic mass.
CT
Circumscribed, lucent, non-enhancing lesion +/- calcification.
MRI
T1WI: circumscribed, hyperintense lesion (isointense to fat)
Treatment and prognosis
Treatment is usually not required. Aspiration/biopsy is not recommended due to inflammatory nature of oil contents.
Differential diagnosis
- fat necrosis
- intramammary lipoma
-
onon ultrasound, an oil cyst and seromaareare often indistinguishable - galactocele
-<p><strong>Oil cysts </strong>in breast imaging refer to <a href="/articles/benign-breast-lesion">benign breast lesions</a> where an area of focal <a href="/articles/fat-necrosis-breast-2">fat necrosis</a> becomes walled off by fibrous tissue. </p><h4>Clinical presentation</h4><ul>-<li>Non-tender palpable lump</li>-<li>asymptomatic</li>-</ul><h4>Pathology</h4><p>Fat debris from ruptured lipocytes tends to conglomerate to form a macroscopic pool of oil surrounded by lipid-laden macrophages or foam cells - known as an oil cyst. The wall can then calcify. Most often this occurs secondary to trauma or surgery; however, this is not always necessary.</p><p>The aetiology of oil cysts is felt to be most often an end-form of liquefaction fat necrosis of the breast resulting from trauma or surgery. However, some oil cysts arise independently, without a prior history of trauma or surgery</p><h5>Associations</h5><ul><li>multiple intradermal oil cysts can be part of <a href="/articles/steatocystoma-multiplex-of-the-breast-1">steatocystoma multiplex</a>-</li></ul><h4>Radiographic features</h4><h5>Mammography</h5><p>Typically seen as a radiolucent rounded mass of fat density +/- wall calcification, which if present typically appears as <a href="/articles/eggshell-calcification-breast-1">eggshell calcification</a>. </p><h5>Ultrasound</h5><p>On ultrasound, most oil cysts are hypo-echoic with smooth walls and show neither posterior acoustic enhancement or shadowing. A very small proportion can represent an intracystic mass.</p><h4>Differential diagnosis</h4><ul>- +<p><strong>Oil cysts </strong>in breast imaging refer to <a href="/articles/benign-breast-lesion">benign breast lesions</a> where an area of focal <a href="/articles/fat-necrosis-breast-2">fat necrosis</a> becomes walled off by fibrous tissue. </p><h4>Epidemiology</h4><p>Occurs across all age and ethnic groups with a female predilection. Usually associated with blunt trauma if present in males.</p><h4>Clinical presentation</h4><ul>
- +<li>usually asymptomatic</li>
- +<li>tender or non-tender palpable lump</li>
- +<li>bruising, if recent trauma</li>
- +</ul><h4>Pathology</h4><p>Fat debris from ruptured lipocytes tends to conglomerate to form a macroscopic pool of oil surrounded by lipid-laden macrophages or foam cells - known as an oil cyst. The wall can then calcify. Most often this occurs secondary to trauma or surgery; however, this is not always necessary.</p><h5>Aetiology</h5><p>The aetiology of oil cysts is felt to be most often an end-form of liquefaction fat necrosis of the breast resulting from trauma or surgery. However, some oil cysts arise independently, without a prior history of trauma or surgery.</p><h5>Macroscopic appearance</h5><p>Specimens are usually obtained from surgical excision or aspiration. Grossly, appears as viscous, oily fluid/material.</p><h5>Microscopic appearance</h5><p>Fat-filled macrophages and foreign body giant cells are usually present. There may be haemorrhage into fat. A fibrous capsule forms around the lipid contents. Following fatty acid saponification, there may be calcific precipitation.</p><h5>Associations</h5><ul><li>multiple intradermal oil cysts can be part of <a href="/articles/steatocystoma-multiplex-of-the-breast-1">steatocystoma multiplex</a>
- +</li></ul><h4>Radiographic features</h4><h5>Mammography</h5><p>Typically seen as a radiolucent rounded mass of fat density +/- wall calcification, which if present typically appears as <a href="/articles/eggshell-calcification-breast-1">eggshell calcification</a>. Lesions are usually well circumscribed with a thin capsule. Rarely, fat-fluid levels may be present.</p><h5>Ultrasound</h5><p>On ultrasound, most oil cysts are hypo-echoic with smooth walls and show neither posterior acoustic enhancement or shadowing. Echogenicity varies. Fat-fluid levels are better characterised sonographically. When present, rim calcifications will demonstrate posterior acoustic shadowing. Complex features include thick walls, mural nodularity, and internal echoic bands. A very small proportion can represent an intracystic mass.</p><h5>CT</h5><p>Circumscribed, lucent, non-enhancing lesion +/- calcification.</p><h5>MRI</h5><p><strong>T1WI</strong>: circumscribed, hyperintense lesion (isointense to fat)</p><h4>Treatment and prognosis</h4><p>Treatment is usually not required. Aspiration/biopsy is not recommended due to inflammatory nature of oil contents.</p><h4>Differential diagnosis</h4><ul>
- +<li>fat necrosis</li>
-<li> on ultrasound, an oil cyst and <a href="/articles/seroma">seroma</a> are often indistinguishable</li>- +<li>on ultrasound, an oil cyst and <a href="/articles/seroma">seroma</a> are often indistinguishable</li>
- +<li>galactocele</li>
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